Prostaglandin E2 receptor subtypes 1 and 2 play a role in TGF-β1-induced renal fibrosis by regulating endoplasmic reticulum stress.

Abstract

This study aimed to investigate the effects of prostaglandin E2 receptor subtypes 1 (EP1) and 2 (EP2) on endoplasmic reticulum (ER) stress induced by TGF-β1 in mouse mesangial cells (MCs) and to explore its potential mechanisms. Mouse mesangial cells were isolated and cultured. EP-siRNAs were transfected into mesangial cells for silencing EP1 and EP2. Mesangial cell proliferation was assessed by the CCK-8 method. Expression of PGE2 was measured by enzyme-linked immunosorbent assay (ELISA). GRP78, TRPC1, ERK1/2, and phospho-ERK1/2 levels were examined by Western blot. TGF-β1 induced mesangial cell proliferation and increased PGE2 secretion. Besides, TGF-β1 significantly upregulated GRP78 and TRPC1 expression at the protein level. Phospho-ERK1/2 protein amounts were also increased (p<0.05). Compared with the TGF-β1 group, cell proliferation in the EP1-siRNA+TGF-β1 group was reduced, while GRP78, TRPC1, and ERK1/2 protein amounts were downregulated (p<0.05). EP1 agonist significantly enhanced above changes and their activities (p<0.05). EP1 antagonist significantly attenuated the above changes (p<0.05). Compared with TGF-β1 group, cell proliferation in EP2-siRNA+TGF-β1 group was increased, while GRP78, TRPC1, and ERK1/2 protein amounts were increased (p<0.05). EP2 agonist significantly attenuated the above changes (p<0.05). EP1 receptor may increase TGF-β1-induced cell damage by increasing the activities of GRP78, TRPC1, and ERK1/2 via ER stress. Meanwhile, the EP2 receptor may reduce TGF-β1-induced cell damage by suppressing GRP78, TRPC1, and ERK1/2 activities, also via ER stress. EP1 inhibition and EP2 stimulation may be a therapeutic option for delaying renal fibrosis.